Shell on Codrut Constantin Gusoi

How to Use: sha256sum

Sun, 02 Apr 2023 16:54:33 +0000

Prerequisites Link to heading

Create a basic file:

echo "abc123" > test123.txt

Digest Link to heading

Find the sha256sum of a file with:

sha256sum test123.txt

You will get the following result:

5ecf8d2cc410094e8b82dd0bc178a57f3aa1e80916689beb00fe56148b1b1256  test123.txt

NOTE: there are 2 spaces between the digest and file name. TWO SPACES!!!

Save that result into a file for easy checking:

sha256sum test123.txt > test123.txt.sha256

Check Link to heading

If there’s a sha256 file available, you can do:

Git init without branch hint

Sat, 14 Jan 2023 13:16:34 +0000

If you run git init you will get this yellow hint:

hint: Using 'master' as the name for the initial branch. This default branch name
hint: is subject to change. To configure the initial branch name to use in all
hint: of your new repositories, which will suppress this warning, call:
hint:
hint:   git config --global init.defaultBranch <name>
hint:
hint: Names commonly chosen instead of 'master' are 'main', 'trunk' and
hint: 'development'. The just-created branch can be renamed via this command:
hint:
hint:   git branch -m <name>

This is annoying, pointless, and a complete waste of the git core developer’s time as well as ours.

Concatenate shell commands

Thu, 13 Oct 2022 08:16:04 +0000

Steps Link to heading

Fetch a command with either:

C-e C-u: go to end of line, cut until beginning of line.
C-a C-k: go to start of line, cut until end of line.

Navigate to older command with:

C-p: previous command.
C-r: search command (use fzf for better results).

Navigate to the end with C-e and type &&.

Now you can paste with C-y.

Result Link to heading

This will turn…

Pretty print Linux $PATH

Sun, 25 Sep 2022 10:19:10 +0000

Bash

echo $PATH | sed "s/:/\n/g"

Shell script infinite loop

Fri, 11 Jun 2021 13:24:23 +0000

Useful for all sorts of things:

while true; do echo 'Inside the loop'; sleep 5; done

Fix docker shell history navigation

Tue, 29 Dec 2020 11:07:12 +0000

Prerequisites Link to heading

Start a docekr container:

docker run --rm -it alpine sh

Run some random commands in that shell:

ls -la
pwd
cd ~
uname -a

Problem Link to heading

Try to navigate the history with Ctrl + p and notice it is broken. When you press it the first time it does nothing, press it a second time it jumps 2 commands.

Basic Makefile CI steps

Sat, 14 Nov 2020 11:59:51 +0000

Create general ci and lint goals for running things with and without docker, and specific ci/* and lint/* goals for individual checks:

#-------------------------------------------------------------------------------
# CI
#-------------------------------------------------------------------------------

# Absolute path to the directory of this Makefile.
HERE = $(realpath $(dir $(realpath $(firstword $(MAKEFILE_LIST)))))

# Run a docker container with the current directory mounted.
DOCKER_HERE := docker run --rm -it -u `id -u`:`id -g` -v "$(PWD)":/here -w /here

.PHONY: ci
ci: ci/editorconfig ci/hadolint ci/yamllint

.PHONY: ci/editorconfig
ci/editorconfig:
	@$(DOCKER_HERE) sdwolfz/editorconfig-checker:latest make lint/editorconfig

.PHONY: ci/hadolint
ci/hadolint:
	@$(DOCKER_HERE) sdwolfz/hadolint:latest make lint/hadolint

.PHONY: ci/yamllint
ci/yamllint:
	@$(DOCKER_HERE) sdwolfz/yamllint:latest make lint/yamllint

#-------------------------------------------------------------------------------
# Lint

.PHONY: lint
lint: lint/editorconfig lint/hadolint lint/yamllint

.PHONY: lint/editorconfig
lint/editorconfig:
	@editorconfig-checker $$(git ls-files)

.PHONY: lint/hadolint
lint/hadolint:
	@hadolint $$(git ls-files | grep Dockerfile)

.PHONY: lint/yamllint
lint/yamllint:
	@yamllint $$(git ls-files | grep -E \.ya?ml$$)

Shell scripts as a package manager

Fri, 30 Oct 2020 21:31:42 +0000

Sometimes code is not available from package managers, just like in the stone age. Until those maintainers wake up to the basic modern programming practices of our glorious present, you can do this:

Create a scripts/sspm.sh file with the code from this repository:

https://gitlab.com/sdwolfz/sspm/-/blob/master/sspm.sh

Create a package specific file scripts/download/footool.sh and use one of those functions:

#!/usr/bin/env sh

set -ex

. ./scripts/sspm.sh

download_from_git                          \
  footool                                  \
  master                                   \
  6f6944bee215d391d7c80c529028003ba3b838da \
  https://gitlab.com/sdwolfz/footool.git

Create an equivalent build file scripts/build/footool.sh to compile it:

#!/usr/bin/env sh
set -ex

APPDIR="$PWD"/lib

cd vendor/footool

./autogen.sh
./configure \
  --prefix="$APPDIR" \
  --enable-bar=yes

make -j`nproc`
make install -j`nproc`

Create a Makefile for easy execution:

.DEFAULT_GOAL = all

# ------------------------------------------------------------------------------
# Package Management

.PHONY: all
all: download clean build

# ------------------------------------------------------------------------------
# Build

.PHONY: build
build: \
	build/footool

.PHONY: build/footool
build/footool:
	@sh scripts/build/footool.sh

# ------------------------------------------------------------------------------
# Clean

.PHONY: clean
clean: \
	clean/footool

.PHONY: clean/footool
clean/footool:
	@rm -f lib/footool

# ------------------------------------------------------------------------------
# Download

.PHONY: download
download: \
	download/footool

.PHONY: download/footool
download/footool:
	@sh scripts/download/footool.sh

Add as many other files and make goals as you want, each for every independent package you need.

Docker Images: basic Node setup

Wed, 14 Oct 2020 18:32:57 +0000

Use this as a template for node apps:

#-------------------------------------------------------------------------------
# Base

FROM node:16.2.0-alpine

SHELL ["/bin/ash", "-c"]

#-------------------------------------------------------------------------------
# Packages

RUN set -exo pipefail              && \
                                      \
    echo 'Install system packages' && \
    apk add --update --no-cache \
      build-base                \
      shadow

#-------------------------------------------------------------------------------
# Workspace

RUN set -exo pipefail       && \
                               \
    echo 'Create workspace' && \
    mkdir -p /work

WORKDIR /work

#-------------------------------------------------------------------------------
# User

ARG HOST_USER_UID=1000
ARG HOST_USER_GID=1000

RUN set -exo pipefail                                  && \
                                                          \
    echo 'Create the notroot user and group from host' && \
    deluser --remove-home node                         && \
    groupadd -g $HOST_USER_GID notroot                 && \
    useradd -lm -u $HOST_USER_UID -g notroot notroot   && \
                                                          \
    echo 'Set direcotry permissions'                   && \
    chown notroot:notroot /work

#-------------------------------------------------------------------------------
# Command

CMD ["sh"]

Build it like this:

Basic Makefile starter

Fri, 17 Jul 2020 18:14:29 +0000

Use this template as a sterter for your Makefile, making sure you intent using tabs as that’s a hard requirement of the make tool.

#-------------------------------------------------------------------------------
# Settings
#-------------------------------------------------------------------------------

# By default the `help` goal is executed.
.DEFAULT_GOAL := help

#-------------------------------------------------------------------------------
# Goals
#-------------------------------------------------------------------------------

.PHONY: help
help:
	@echo 'Usage: make [<GOAL_1>, ...] [<VARIABLE_1>=value_1, ...]'
	@echo ''
	@echo 'Examples:'
	@echo '  make'
	@echo '  make help'
	@echo ''
	@echo 'Goals:'
	@echo '  - help: Displays this help message.'
	@echo '  - here: Displays the directory where this Makefile is located.'
	@echo ''
	@echo 'Default Goal: help'
	@echo ''

Docker Images: basic Ruby setup

Thu, 16 Jul 2020 18:51:03 +0000

Use this as a template for ruby apps:

#-------------------------------------------------------------------------------
# Base

FROM ruby:2.7.2-alpine

SHELL ["/bin/ash", "-c"]

#-------------------------------------------------------------------------------
# Packages

RUN set -exo pipefail              && \
                                      \
    echo 'Install system packages' && \
    apk add --update --no-cache \
      build-base                \
      shadow

#-------------------------------------------------------------------------------
# Workspace

RUN set -exo pipefail       && \
                               \
    echo 'Create workspace' && \
    mkdir -p /work

WORKDIR /work

#-------------------------------------------------------------------------------
# User

ARG HOST_USER_UID=1000
ARG HOST_USER_GID=1000

RUN set -exo pipefail                                  && \
                                                          \
    echo 'Create the notroot user and group from host' && \
    groupadd -g $HOST_USER_GID notroot                 && \
    useradd -lm -u $HOST_USER_UID -g notroot notroot   && \
                                                          \
    echo 'Set direcotry permissions'                   && \
    chown notroot:notroot /work

#-------------------------------------------------------------------------------
# Gems

COPY --chown=notroot:notroot Gemfile* /work/

USER notroot

RUN set -exo pipefail                 && \
                                         \
    echo 'Install gems'               && \
    cd /work                          && \
    bundle install --jobs 3 --retry 3

#-------------------------------------------------------------------------------
# Command

CMD ["sh"]

Build it like this:

Docker Images: basic entrypoint

Tue, 14 Jul 2020 21:24:54 +0000

This is a docker entrypoint script that loads environment variables from a mounted file and executes the given command; most of the time it’s all you need.

#!/bin/sh

set -e

# Load environment variables.
if [ -f /environment/secrets.env ];
then
  set -a
  echo 'Sourcing: /environment/secrets.env'
  . /environment/secrets.env
  set +a
fi

# Executes the given command.
exec "$@"

Give this file a short and simple name like entry and copy it in your Dockerfile: